Reinforced stabilisation strip for reinforced embankment structures, with a functionalised casing

ABSTRACT

The invention relates to a reinforced stabilisation strip ( 1 ) for reinforced embankment structures, comprising long reinforcing fibres ( 12 ) and a longitudinal casing ( 11 ) surrounding or enclosing the long reinforcing fibres ( 12 ), the casing ( 11 ) at least partially consisting of a functionalised polymer material ( 111 ) comprising a functionalised polyolefin. The invention also relates to a reinforced embankment structure ( 1 ) comprising such a stabilisation strip ( 1 ), and to a method for the production thereof.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to the technical field of thereinforcement of ground for constructing retaining walls. In particular,it relates to a stabilisation strip, also referred to as a geostrip,which is reinforced and can be used for structures made of reinforcedsoil or reinforced earth for constructing retaining walls.

PRIOR ART

A reinforced embankment structure comprises an embankment, a facing andreinforcements, connected or not to the facing.

The embankment is composed of a mixture or assembly that may comprise atleast one material from sand, gravel, fine earth, crushed rocks,recycled material such as materials from demolition of buildings orcivil engineering structures, industrial residues or binders such aslime or cement.

The facing provides the aesthetic appearance and stability of thestructure with respect to erosion by covering the front face of theretaining wall, i.e. the invisible face. It is usually produced usingjuxtaposed prefabricated concrete elements, in the form of slabs orblocks. It may also consist of metallic welded lattice panels or gabionsmade of woven metal wires.

The reinforcements may be made of various materials, such as metal (andmore particularly galvanised steel) and synthetic materials. They aredisposed within the embankment with a density depending on the stressesthat may be exerted on the structure, the thrust forces from the landbeing absorbed by friction between the embankment and thereinforcements.

In the great majority of cases, the reinforcements are provided in theform of stabilisation strips having a length of approximately 3 m to 10m, although shorter or longer strips may be used. The width of thestrips is generally between 4 cm and 10 cm, although it is possible touse strips with a width ranging up to 10 cm or 25 cm, or even more. Thethickness varies, for example from approximately 1 mm to a fewcentimetres and is generally between 1 mm and 6 mm. These stabilisationstrips transmit the forces within the embankment, thus distributing theforces.

In particular, it is necessary to transmit the forces between astabilisation strip and the embankment in which it is placed. Moreover,it is preferable for the stabilisation strip to be capable oftransmitting the forces over its entire length.

One solution known to the person skilled in the art consists in usingstabilisation strips comprising a longitudinal sheath that interactswith the embankment by friction. The stabilisation strips also comprisesa reinforcement composed of a set of fibres disposed longitudinally,parallel to one another and embedded inside the sheath in its centralpart so as to reinforce the tensile strength. The sheath is generallymade of polyethylene, and the fibres of polyester. When necessary, asolution known to the person skilled in the art for increasing frictionresistance between the strips and the embankment consists in providingthe longitudinal sheath with a central part comprising the reinforcementfibres and projecting lateral parts in order better to interact with thegrains constituting the embankment.

Polyester fibres have the drawback of being sensitive to surroundingalkalinity and may degrade when the stabilisation strips that enclosethem are used for example in basic soils. This is for example the casewith fine soils treated with lime or hydraulic binders for improvingtheir workability and/or stability.

Thus it is advantageous to be able to use other types of fibre that arenot very sensitive to the nature of the embankment; for examplepolyvinyl alcohol fibres.

The inventors have attempted to produce stabilisation strips comprisinga polyethylene sheath and a reinforcement composed of a set of polyvinylalcohol fibres.

During some adhesion tests between these stabilisation strips and theembankment, under strong embankment confinements, it has happened thatthe fibres slide within the sheath where the strip should keep itsintegrity and that that the strip is caused to slide with respect to theembankment surrounding it. It was concluded therefrom that the absenceof a chemical bond between the polyethylene sheath and polyvinyl alcoholfibres led to insufficient adhesion strength between the fibres and thesheath.

Presentation of the Invention

The present invention therefore seeks to overcome the drawbacks of theprior art described above. In particular, the present invention seeks tomake it possible to produce stabilisation strips that are not sensitiveto their environment (and preferably able to be used for various typesof embankment) while having high tensile strength and being able tomeasure their mechanical properties reliably.

To this aim, the present invention provides a reinforced stabilisationstrip for reinforced embankment structures, comprising longreinforcement fibres and a longitudinal sheath surrounding or enclosingthe long reinforcement fibres, the sheath being at least partially madefrom a functionalised polymeric material comprising a functionalisedpolyolefin.

The polyolefin functionalisation makes it possible to provide thefunctionalised polymeric material of the sheath with functional groupswith which the material of the reinforcement fibres can react, thuscreating bonds between the reinforcement fibres and the sheath thatprevent disconnection thereof by increasing the adhesion force betweenthe reinforcement fibres and the sheath.

Other optional and non-limiting features are presented below.

The functionalised polyolefin advantageously comprises 0.01 wt. % to 45wt. % functionalisation.

The functionalised polymeric material may comprise a mixture ofnon-functionalised polymer and functionalised polyolefin. Preferably,the non-functionalised polymer is a non-functionalised polyolefin.Preferably, the non-functionalised polyolefin is a non-functionalisedpolyethylene, still preferably a non-functionalised linear low-densitypolyethylene. The mass ratio between functionalised polyolefin andnon-functionalised polymer is between 1:9 and 10:0.

The functionalised polymeric material advantageously has afunctionalisation gradient with a maximum at contact with thereinforcement fibres and which decreases gradually and away from thereinforcement fibres.

In a particular embodiment of the invention, the functionalisedpolyolefin is a polyolefin substituted by a chemical element having afunctional group chosen from mono- or di-carboxylic acid anhydrides oron which the chemical element has been grafted. Preferably, the chemicalelement is a maleic anhydride or a phthallic anhydride group or anacrylic acid.

The sheath may further comprise a non-functionalised zone surrounding orenclosing the functionalised polymeric material. This non-functionalisedzone is a non-functionalised polymer, for example the samenon-functionalised polymer of the mixture forming the functionalisedpolymeric material, or other.

The reinforcement fibres are advantageously made of a material chosenfrom polyvinyl alcohol, polyesters, silica glass, linear or aromaticpolyamides and metals. The reinforcement fibres may be in the form ofthreads, strands or cords; these threads, strands or cords may be spunor woven.

The sheath may further comprise at least one longitudinal edge free fromreinforcement fibres and having notches.

The stabilisation strip may have two longitudinal ends joined to eachother, thus adopting the form of a loop.

The present invention also proposes a stabilisation layer made at leastpartly of stabilisation strips as described above. This stabilisationlayer may be in the form of a geogrid formed by a warp and a weftcomposed of stabilisation strips (1), the warp and weft being woven orsuperimposed one on the other. The stabilisation strips of the warp andweft are connected at certain intersection points by hot welding oradhesive bonding.

The present invention also proposes a reinforced embankment structurecomprising:

-   -   fill; and    -   at least one stabilisation strip as described above, and/or at        least one stabilisation layer also described above, said at        least one stabilisation strip and/or said at least one        stabilisation layer being disposed substantially horizontally on        one or more levels in the embankment.

This reinforced embankment structure may further comprise a facing andconnectors for connecting at least some of the stabilisation stripsand/or stabilisation layers to the facing. These connectors may also beformed by stabilisation strips, in particular those having a loop form.

Finally, the present invention provides a method for manufacturing astabilising strip as described above, said method comprising:

-   -   heating the functionalised polymeric material to at least the        activation temperature of the functional group;    -   shaping the functionalised polymeric material around the        reinforcement fibres in order to form the sheath surrounding or        enclosing the reinforcement fibres.

The method may further comprise drawing the reinforcement fibres, andshaping the functionalised polymeric material may be carried out byextruding the functionalised polymeric material around the reinforcementfibres.

The method may also comprise heating the non-functionalised polymer anddrawing the reinforcement fibres;

in which shaping the functionalised polymeric material is carried out byco-extruding the functionalised polymeric material around thereinforcement fibres and the non-functionalised polymer around thefunctionalised polymeric material forming the non-functionalised zone ofthe sheath surrounding or enclosing the functionalised polymericmaterial.

Drawing the reinforcement fibres is advantageously carried out as thesheath is extruded.

DRAWINGS

Other objectives, features and advantages will become apparent from areading of the following detailed description with reference to thedrawings given by way of illustration and non-limitatively, among which:

FIG. 1 is a schematic illustration of a stabilisation strip accordingthe invention, the sheath of which is entirely made of functionalisedpolymeric material;

FIG. 2 is a schematic illustration of a stabilisation strip according tothe invention, the sheath of which comprises a non-functionalised zonesurrounding or enclosing the functionalised polymeric material;

FIG. 3 is a schematic illustration of a stabilisation strip according tothe invention, the sheath of which is entirely made of functionalisedpolymeric material and has notches;

FIG. 4 is a schematic illustration of a stabilisation strip according tothe invention, the sheath of which comprises a non-functionalised zonesurrounding or enclosing the functionalised polymeric material and hasnotches;

FIG. 5 is a schematic illustration of a stabilisation layer comprising awarp made of stabilisation strips and a weft made of stabilisationstrips placed on top one another;

FIG. 6 is a schematic illustration of a stabilisation layer comprising awarp made of stabilisation strips and a weft made of stabilisationstrips, the warp and the weft being woven to one another, this type ofconfiguration corresponds to the definition of a reinforcement geogrid;

FIG. 7 is a schematic illustration of a reinforced embankment structurethat can be produced with stabilisation strips of one of FIGS. 1 to 4,alternatively with layers of FIG. 5 or 6;

FIG. 8 is a flow chart illustrating the various steps of the method formanufacturing a stabilisation strip according to the present invention;

FIG. 9 is a schematic illustration of a stabilisation strip cut out andused for measuring the adhesion force between the reinforcement fibresand the sheath.

DETAILED DESCRIPTION OF THE INVENTION

With reference to FIGS. 1 to 4, a reinforced stabilisation strip for areinforced embankment structure according to the invention is describedbelow.

This stabilisation strip 1 comprises long reinforcement fibres 12 and alongitudinal sheath 11 surrounding or enclosing the long reinforcementfibres 12. The sheath 11 is at least partially made from afunctionalised polymeric material comprising a functionalised polyolefin(Po-f).

A polyolefin is a saturated aliphatic polymer, optionally substituted,obtained from polymerising an olefin (also referred to as an alkene).

The functionalised polyolefin can be chosen from functionalisedpolyethylenes, functionalised polypropylenes or functionalised olefiniccopolymers such as functionalised ethylene vinyl acetate (EVA).Preferably functionalised polyethylenes and in particular functionalisedlinear low-density polyethylene will be chosen.

The term “functionalisation” will be understood in the context of thepresent invention to designate a modification of the polyolefin bysubstituting it with a chemical element comprising a functional group oran insaturation or by grafting the chemical element onto the polyolefin.Modification of the polyolefin may also lead to the creation of aninsaturation in the polyolefin chain. The functional group for its partis capable of reacting with the material of the reinforcement fibres 12,by creating covalent bonds or hydrogen bonds with it.

In particular, the functional group may be chosen from mono- ordi-carboxylic acid anhydrides.

For example, the chemical element substituting a hydrogen atom in thecarbon chain of the polyolefin may be: a maleic anhydride or phthalicanhydride group or an acrylic acid; the maleic anhydride group being themost generally used.

It is not necessary to provide a large number of functional groups inthe Po-f. Indeed functionalisation of the Po-f is generally between 0.01wt. % and 45 wt. %. Beyond 45 wt. % functionalisation, it is no longer apolyolefin. Advantageously, the functionalisation degree is between 0.01wt. % and 30 wt. %, preferably between 0.01 wt. % and 15 wt. %, orpreferably between 0.01 wt. % and 5 wt. %, still preferably between 0.1wt. % and 2 wt. %.

The functionalisation degree of the Po-f must be understood as the ratiobetween the mass of functional groups that have reacted with thepolyolefin and the total mass of functionalised polyolefin Po-f. It canalso be calculated by the gain in mass between the non-functionalisedinitial polyolefin (Po-nf) and the functionalised polyolefin Po-f. Forexample, if 10 g of maleic anhydride has reacted with a polyolefin andthe total mass of the Po-f is 100 g, then the degree offunctionalisation is 10 wt. % by mass. The functionalised polymericmaterial may comprise 100 wt. % of Po-f or a mixture of Po-f andnon-functionalised polymer. This non-functionalised polymer is a polymercompatible with the functionalised polyolefin, that is to say theirmixture is stable over time and no phase separation is observable. Theyare said to be totally miscible. The non-functionalised polymer ispreferably chosen from non-functionalised polyethylenes (PE-nf),non-functionalised polypropylene (PP-nf) or olefinic copolymers such asethylene vinyl acetate (EVA-nf). The preferred non-functionalisedpolymer is linear low-density polyethylene (LLDPE-nf).

Advantageously, the mass ratio between Po-f and non-functionalisedpolymer is between 1:9 and 10:0. The mass ratio between Po-f, preferablyLLDPE-f and non-functionalised polymer, preferably LLDPE-nf, may bebetween 1:4 and 1:1.

The functionalised polymeric material 111 may have a functionalisationgradient with a maximum at contact with the reinforcement fibres 12 andwhich decreases gradually and away from the reinforcement fibres 12. Thegradient may be continuous or in steps.

The sheath 11 may also comprise a non-functionalised zone 112surrounding or enclosing the functionalised polymeric material 111. Thusthe cost of the sheath 11 can be reduced since, in general,non-functionalised polymer (or Po-nf) is less expensive than Po-f. Thepolymer of the non-functionalised zone may be the same as that of themixture becoming the functionalised polymeric material or different, andchosen from those mentioned above for the mixture.

One or more channels 13 may be formed inside the sheath 11, thereinforcement fibres 12 being drawn inside these channels 13. Increasingthe number of channels 13 makes it possible to increase the surface areaof contact between the long reinforcement fibres 12 and the sheath 11,and consequently the interaction strength between these two constituentelements. Preferably, the number of channels is between 5 and 20.

The reinforcement fibres 12 consist of any material enabling increase inthe tensile strength of the stabilisation strip. They are advantageouslymade of material chosen from polyvinyl alcohol (PVAL), polyesters,silica glass, linear or aromatic polyamides (also referred to asaramids) and metals, or a mixture thereof. If two or more materials areused, the reinforcement fibres made of one given materials may begrouped together, or the composition of reinforcement fibres in each ofthe channels 13 may be different from that of another, but preferablythe composition of reinforcement fibres is the same in each of thechannels 23.

Among the fibres mentioned, PVAL fibres are preferred. This is because,unlike polymers, glass, linear polyamides, aramids and metals, thesematerials are not sensitive to the nature of the fill (and particularlythe pH of the soil forming part of the composition of the fill).

The reinforcement fibres 12 are advantageously disposed in the sheath 11parallel to the length thereof, and parallel to one another. They may beraw, i.e. not spun.

The reinforcement fibres 12 may also be present in the form of threadsparallel to one another. A “thread” results from the spinning of fibres.That is to say the fibres are all oriented to the same direction andtwisted together. A thread composed of fibres has a higher tensilestrength than all the fibres merely put alongside one another; indeed,the spinning reinforces the mechanical properties of the fibres.

The reinforcement fibres 12 may also be present in the form of strandsor cords parallel to one another, as described in document EP 2171160.The spinning or braiding of several threads together gives a “strand”.The spinning or braiding of several strands together gives a “cord”.Because of the fact that the strand and cord result from an assembly ofa plurality of threads, the appearance of their surface is not as smoothas that of fibres or threads. Consequently a strand or cord has asurface relief, i.e. their surface has recesses and bulges. Thefunctionalised polymeric material surrounding or enclosing thereinforcement fibres 12 fits to the shape of these recesses and bulges,thus making it possible to add mechanical strength to the tensilestrength, further increasing the adhesion force between thereinforcement fibres 12 and the sheath 11.

The reinforcement fibres 12 may also be composed of a mixture comprisingat least two elements from raw fibres, threads, strands and cords.

The sheath 11 may comprise at least one high-adhesion longitudinal edge113 free from the reinforcement fibres and having notches 114 (see FIGS.3 and 4), as described in document EP 2247797. The function of thenotches 114 on this high-adhesion longitudinal edge 113 is to rubagainst the fill of the reinforced embankment structure in order to holdthe stabilisation strip 1 in place.

In general terms, and as already mentioned above, the stabilisationstrip 1 has a length of approximately 3 m to 10 m, although longer orshorter stabilisation strips 1 may also be provided. The width of thestabilisation strip 1 is between 4 cm and 6 cm, although it is possibleto manufacture strips with a greater width ranging up to 10 cm or even25 cm. The thickness of the stabilisation strip 1 varies between 1 mmand a few centimetres, but preferentially between 1 mm and 6 mm.

The stabilisation strip 1 may have two longitudinal ends joined to eachother, thus taking the form of a loop. Such a loop made of astabilisation strip may be used as a connector for connecting thestabilisation strips to the facings of the reinforced embankmentstructure. Preferably, the circumference of the loop is between 40 cmand 80 cm.

A plurality of stabilisation strips 1 may form at least part of astabilisation layer 10, advantageously in the form of a geogrid formedby a warp comprising stabilisation strips and a weft also comprisingstabilisation strips. The warp and weft are superimposed (FIG. 5) orwoven (FIG. 6). In the case of superimposed warp and weft, some or allof the stabilisation strips 1 c of the warp are fixed to thestabilisation strips 1 t of the weft crossing them at intersections 101.In the case of woven warp and weft, this partial or total fixing of thestabilisation strips 1 c of the warp to the stabilisation strips 1 t ofthe weft may be provided, but is not required; this is because weavingenables the warp to be held with respect to the weft and vice versa. Thestabilisation strips 1 c of the warp are preferentially disposed at 90°to the stabilisation strips 1 t of the weft, crossing the latter atright angles. However, the invention is not limited to this orientationand any other relative orientation of the stabilisation strips 1 c ofthe warp with respect to the stabilisation strips 1 t of the weft arepossible, for example 60° and 45°.

The stabilisation strips 1 c of the warp and the stabilisation strips 1t of the weft may be fixed by hot welding or adhesive bonding. The knownwelding methods for the polyolefin sheaths are hot air welding, mirrorwelding, hot wedge welding, ultrasonic welding and infrared welding.

The stabilisation strip 1 described above is used in the construction ofreinforced embankment structures 2 (FIG. 7). Such a reinforcedembankment structure 2 comprises, in addition to the stabilisationstrips 1, fill 21. The stabilisation strips 1 are disposed horizontallyin the fill on one or more levels. In a variant or in addition, thesestabilisation strips 1 may form a stabilisation layer 10 disposedhorizontally in the fill on one or more levels.

The fill 21 generally comprises a mixture or assembly that may compriseat least one material from sand, gravel, fine soil, crushed rocks,recycled materials such as materials from demolition of buildings orcivil-engineering structures, industrial residues or binders such aslime or cement.

Generally, such a reinforced embankment structure 2 also comprises afacing 22 and connectors 23 for connecting at least some of thestabilisation strips 1 to the facing 22. The facing 22 may be producedfrom prefabricated juxtaposed elements 221 made from concrete, in theform of slabs or blocks. It may also consist of metal welded latticepanels or gabions made of woven metal wires.

The stabilisation strips 1 may be used as they are, that is to say theyare individually disposed during construction of the reinforcedembankment structure 2.

When the stabilisation strips 1 are in the form of stabilisation layers10, a whole set of stabilisation strips 1 is disposed in one operationduring construction of the reinforced embankment structure 2. Theadvantage is a saving in time for laying the stabilisation strips 1compared with individual placing. Another advantage is an easier layingsince the distance between the stabilisation strips 1 is defined inadvance during manufacturing of the stabilisation layer 10.

The connectors 23 may be stabilisation strips 1, in particular in theform of loops made by winding and assembling. In such case, the adhesionbetween the threads and the sheath is essential in order to ensure thestrength of the loop.

With reference to FIG. 8, a method for manufacturing a stabilisationstrip is described below.

The method for manufacturing a stabilisation strip as described abovecomprises:

-   -   heating the functionalised polymeric material at least to the        activation temperature of the functional group of the Po-f; and    -   shaping the functionalised polymeric material around        reinforcement fibres in order to form the sheath surrounding or        enclosing the reinforcement fibres, thus obtaining the        stabilisation strip.

The activation temperature is the temperature at which the functionalgroup is activated and depends on the nature of the chemical elementfunctionalising the polyolefin. For example, the activation temperaturefor maleic anhydride is 180° C. Thus, advantageously, the polymericmaterial functionalised by maleic anhydride is heated to approximately180° C. for a few seconds in an extruder or mixer.

The method advantageously comprises drawing the reinforcement fibres ina drawing direction. Shaping the functionalised polymeric material iscarried out by extruding the functionalised polymeric material aroundreinforcement fibres in the drawing direction.

This embodiment is advantageously used for a uniform sheath, i.e. asheath without any non-functionalised zones.

In a variant, shaping the functionalised polymeric material is carriedout so as to form a functionalised gradient in the polymeric materialwith a maximum at contact with the reinforcement fibres and whichdecreases gradually away from the reinforcement fibres.

In addition, the method may comprise heating a non-functionalisedpolymer, preferentially PE-nf, and more preferentially still LLDPE-nf.Shaping the functionalised polymeric material is carried out byco-extruding the functionalised polymeric material around reinforcementfibres and the non-functionalised polymer around functionalisedpolymeric material in order to form the non-functionalised zone of thesheath surrounding or enclosing the functionalised polymeric material.

Drawing the reinforcement fibres may be carried out as the sheath isextruded, affording a saving in time and a saving in space formanufacturing the stabilisation strip.

Prior to the drawing of the reinforcement fibres, the latter may havebeen spun into threads. The threads may have been spun or braided intostrands and the strands may have been spun or braided into cords.

Alternatively, the reinforcement fibres are already supplied in the formof threads, strands or cords, optionally previously drawn. Optionally,the fibres supplied in the form of threads or strands may be spun orbraided to give respectively strands or cords.

Test—Measurement of the Adhesion Force Between the Reinforcement Fibresand the Sheath

The test presented below is carried out on stabilisation stripscomprising a sheath and a functionalised polymeric material comprising amixture of LLDPE-nf and LLDPE-f in proportions as indicated in table 1.The LLDPE-f has a functionalisation degree estimated at approximately 1wt. % with maleic anhydride elements. A control example is also providedfor comparison. The sheath in this control example comprises 100%LLDPE-nf.

TABLE 1 Example 1 Example 2 Example 3 Example 4 Control Mass ratio 25:7550:50 75:25 100:0 0:100 of LLDPE-f and LLDPE-nf

The stabilisation strips 1 comprise a PVAL reinforcement in the form ofstrands present inside the sheath. The PVAL reinforcement fibres aredistributed in five channels 13 inside the sheath 11, the centralchannel 131 of which is 7 mm wide and 2 mm high. The shape andconstitution of the stabilisation strips are identical for all thetested mass ratios of LLDPE-f to LLDPE-nf and for the control example.

A cut En is made on two opposite metal edges of the stabilisation strip,leaving only the central channel 131 intact. At 10 cm from the cut edge,a transverse incision In is made through the central channel 131 overthe whole of its width, thus severing the strands situated in thecentral channel 131. Thus, between the cut En and the incision In, thestabilisation strip 1 is left intact over 10 cm (see FIG. 9).

Each stabilisation strip 1 thus prepared is disposed on a uniaxialtraction bench. The two ends of the strip are fixed to the bench and atraction force is applied between both ends so as to separate both endsat a speed of 200 mm/min. The force needed for the separation at 200mm/min is recorded.

Thus, it was possible to measure the adhesion force between thereinforcement fibres and the sheath 11 over a length of 10 cmcorresponding to a contact surface between the reinforcement fibres andthe sheath 11 of 1800 mm². The results are recorded in following table2:

TABLE 2 Exam- Exam- Exam- ple 1 ple 2 ple 3 Example 4 Example C Adhesionforce 2140 2908 3072 2960 1368 (N) Gain % 56% 113% 125% 116% 0% Adhesionforce 0.43 0.86 0.95 0.88 0 per unit surface (N/mm² = (MPa)

It is thus observed that, compared with a stabilisation strip with asheath made entirely of LLDPE-nf, the gain in adhesion force is already56% for a sheath with a functionalised polymeric material comprising 25%LLDPE-f. This gain climbs to more than 110% for stabilisation stripswith a sheath with a functionalised polymeric material comprising 50%,75% and 100% LLDPE-f.

1. A reinforced stabilisation strip for reinforced embankmentstructures, comprising long reinforcement fibres and a longitudinalsheath surrounding or enclosing the long reinforcement fibres, thesheath being made at least partially from a functionalised polymericmaterial comprising a functionalised polyolefin.
 2. The stabilisationstrip of claim 1, wherein the functionalised polyolefin comprises 0.01wt. % to 45 wt. % functionalisation.
 3. The stabilisation strip of claim1, wherein the functionalised polymeric material comprises a mixture ofnon-functionalised polymer and functionalised polyolefin.
 4. Thestabilisation strip of claim 3, wherein the mass ratio of functionalisedpolyolefin to non-functionalised polymer is between 1:9 and 10:0.
 5. Thestabilisation strip of claim 1, wherein the functionalised polymericmaterial has a functionalisation gradient with a maximum at contact withthe reinforcement fibres and which decreases gradually and away from thereinforcement fibres.
 6. The stabilisation strip of claim 1, wherein thefunctionalised polyolefin is a polyolefin substituted by a chemicalelement having a functional group chosen from mono- or di-carboxylicacid anhydrides or on which the chemical element has been grafted. 7.The stabilisation strip of claim 6, wherein the chemical element is amaleic anhydride or phthalic anhydride group or an acrylic acid.
 8. Thestabilisation strip of claim 1, wherein the sheath comprises anon-functionalised zone surrounding or enclosing the functionalisedpolymeric material.
 9. The stabilisation strip of claim 1, wherein thereinforcement fibres are made of a material chosen from polyvinylalcohol, polyesters, silica glass, linear or aromatic polyamides andmetals.
 10. The stabilisation strip of claim 1, wherein thereinforcement fibres are in the form of threads, strands or cords; thesethreads, strands or cords being spun or braided.
 11. The stabilisationstrip of claim 1, wherein the sheath comprises at least one longitudinaledge free from reinforcement fibres and having notches.
 12. Astabilisation layer produced at least partly with stabilisation stripscomprising long reinforcement fibres and a longitudinal sheathsurrounding or enclosing the long reinforcement fibres, the sheath beingmade at least partially from a functionalised polymeric materialcomprising a functionalised polyolefin.
 13. The stabilisation layer ofclaim 12, in the form of a geogrid with a warp and a weft, the warp andthe weft being partly composed of stabilisation strips, the warp and theweft being woven or superimposed one on the other.
 14. The stabilisationlayer of claim 13, in which the stabilisation strips of the warp andweft are connected at certain intersection points by hot welding oradhesive bonding.
 15. A reinforced embankment structure comprising:fill; and at least one stabilisation strip comprising long reinforcementfibres and a longitudinal sheath surrounding or enclosing the longreinforcement fibres, the sheath being made at least partially from afunctionalised polymeric material comprising a functionalised polyolefinand/or at least one stabilisation layer produced at least partly withstabilisation strips comprising long reinforcement fibres and alongitudinal sheath surrounding or enclosing the long reinforcementfibres, the sheath being made at least partially from a functionalisedpolymeric material comprising a functionalised polyolefin, said at leastone stabilisation strip and/or said at least one stabilisation layerbeing disposed substantially horizontally on one or more levels in theembankment.
 16. The reinforced embankment structure of claim 15, furthercomprising a facing and connectors for connecting at least some of thestabilisation strips to the facing.
 17. A method for manufacturing astabilisation strip comprising long reinforcement fibres and alongitudinal sheath surrounding or enclosing the long reinforcementfibres, the sheath being made at least partially from a functionalisedpolymeric material comprising a functionalised polyolefin, the methodcomprising: heating the functionalised polymeric material to at leastthe activation temperature of the functional group of the functionalisedpolyolefins; and shaping the functionalised polymeric material aroundthe reinforcement fibres in order to form the sheath surrounding orenclosing the reinforcement fibres thus obtaining the stabilisationstrip.
 18. The method of claim 17, comprising: drawing the reinforcementfibres; shaping the functionalised polymeric material being carried outby extruding the functionalised polymeric material around thereinforcement fibres.
 19. The method of claim 17, wherein: the methodfurther comprises heating non-functionalised polymer and drawing thereinforcement fibres; wherein shaping the functionalised polymericmaterial is carried out by co-extruding the functionalised polymericmaterial around the reinforcement fibres and the non-functionalisedpolymer around the functionalised polymeric material thus forming thenon-functionalised zone of the sheath surrounding or enclosing thefunctionalised polymeric material.
 20. The method of claim 18, whereindrawing the reinforcement fibres is carried out as the sheath isextruded.